A printing system has been designed which takes advantage of a spatial light modulator device to create a very simple exposure unit. The system uses a conventional light source such as a tungsten halogen light, and which is focused onto a deformable mirror device (DMD) consisting of a row or rows of individually deformable mirrors constructed on a single substrate.
The DMD is arranged in conjunction with a lens such that in the undeflected state, light reflecting from each mirror has a reflection angle such that the light is directed away from the remaining elements of the printing system. When a particular mirror is otherwise deflected, the angle of light reflection changes, and the light is then passed through the remaining system. The reflected light may, for instance, be directed to a photo receptor drum of a standard xerographic print process.
Present semi-conductor manufacturing processes are able to achieve DMD widths of up to 20 millimeters, containing approximately one thousand individual mirrors. These densities result in DMDs capable of illuminating a three-inch long strip at approximately 300 dots per inch (dpi) which is letter quality. Most printing applications, however, use formats wider than three inches. This requires a system designer to either lengthen the traditional 20 millimeter DMD row or to magnify the projected array such that a print density of less than 300 dpi results. The first alternative, producing an extended DMD, though theoretically possible, is prohibitively expensive. Producing a long DMD increases fabrication complexity of the DMD, poses difficult problems of uniform illumination, and often results in a non-uniform image even when properly illuminated. The second alternative, reducing the pixel print density, is not acceptable in those applications requiring letter quality print output.
Therefore, a need has arisen for a deformable mirror device system which is capable of illuminating an extended strip and which is easy to fabricate, illuminate and which results in uniform projections.